<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
<script>

var str="Hello world!"
alert(str.indexOf('hello'));		//	-1
alert(str.indexOf('World'));		//	-1
alert(str.indexOf('world'));		//	6


</script>
</body>
</html>